The present invention relates to patient monitoring apparatus such as fetal monitoring apparatus, and more particularly to a novel wireless patient monitoring apparatus that uses low frequency inductive coupling.
Apparatus for the real-time monitoring of physiological conditions in medical patients is well known. Examples of such apparatus include electrocardiogram recorders, heart rate monitors, electroencephalograph apparatus, maternal uterine activity monitors, and various other noninvasive medical instrumentation. Technology for monitoring such physiological functions includes ultrasound and tocodynamometer (TOCO) transducers. One type of instrumentation that benefits from the use of both ultrasound and tocodynamometer transducers is a fetal monitor, such as the Model IM77 Intrapartum Fetal Monitor manufactured by Advanced Medical Systems, Inc. of Hamden, Conn., U.S.A. This fetal monitor measures and records maternal and fetal activity during pregnancy through labor and delivery. Data on the fetal heart rate (FHR) and uterine activity (UA) is displayed on a front panel and simultaneously recorded on a trace (strip chart) recorder. FHR can be measured externally using Doppler ultrasound. Uterine activity can be measured externally using a TOCO transducer that incorporates, e.g., a strain gauge.
A disadvantage with prior patient monitoring systems, such as fetal monitors, is that the various transducers used to detect physiological functions required electrical cables in order to communicate the transducer signals to a console containing the user interface, analysis circuitry and output devices (e.g., strip chart recorder) used by medical professionals. Often, such cables become tangled, interfere with other medical procedures, and typically get in the way of the patient wearing them. Moreover, the need to be connected by cables limits the mobility of the patient and can cause discomfort. Additionally, wired transducers which are connected to a console that contains potentially dangerous electrical currents are not able to be used in underwater deliveries, due to safety concerns.
Past attempts to overcome the problems inherent with cabled transducers have focused on using telemetry (i.e., radio frequency signals) to provide wireless transducers. Although RF telemetry is advantageous in certain respects (such as a long range of operation which facilitates patient mobility), it also has various disadvantages in certain applications. For example, where different patients are being monitored in the same hospital, each monitor will have to operate at a different frequency to avoid conflict. Telemetry is also relatively costly to implement due to various transmitter and receiver requirements and the fact that government approval (e.g., by the Federal Communications Commission--FCC) is typically required. Telemetry fetal monitoring systems are also not well suited to underwater deliveries.
It would be advantageous to provide a wireless patient monitoring system that avoids the disadvantages of cabled transducers as well as the disadvantages of prior art telemetry systems. Such apparatus should be compact (a particular advantage for use with fetal monitors to be used in underwater deliveries) easy to use, and reliable.
The present invention provides a wireless patient monitoring system enjoying the aforementioned and other advantages.